Are they considered to be rude when speaking Hebrew? English? Some other language? Accent relevant? Anything religious whatsoever relevant? Is the fact that Hebrew uses a different alphabet relevant? Thiat it's written from right to left? Do the Israelis fail to follow what is considered standard etiquette in foreign shops? Do they fail to use certain words? Or phrases? Because they don't exist in Hebrew?

Are they considered to be rude when speaking Hebrew? No English? Yes Some other language? Could be this too. Accent relevant? No Anything religious whatsoever relevant? No Is the fact that Hebrew uses a different alphabet relevant? No Thiat it's written from right to left? No Do the Israelis fail to follow what is considered standard etiquette in foreign shops? YesDo they fail to use certain words? See next answer. Or phrases? Yes Because they don't exist in Hebrew? Yes!

Are these phrases that don't exist in Hebrew used specifically in shops? Mostly, assuming you broadly define "shops" to include any place of business that sells things directly to customers, though they could be used in other contexts. Is it something related to numbers? No Money? No Goods?Not specifically, although goods would likely be involved in the relevant situations.

Is this mainly an issue of tone/politesse? By which I mean adjusting the tense or speech pattern to show politeness, such as using 'I want' instead of 'I would like'?

Or something similar to the way requests/instructions in French would use the imperative even when issuing the request politely, whereas a polite English speaker would phrase it in the vein of 'Could you please <x>?'

Is this mainly an issue of tone/politesse? By which I mean adjusting the tense or speech pattern to show politeness, such as using 'I want' instead of 'I would like'? In fact, this is exactly what they do.

Or something similar to the way requests/instructions in French would use the imperative even when issuing the request politely, whereas a polite English speaker would phrase it in the vein of 'Could you please <x>? In Hebrew, they would say "I want X."

***SPOILER****

You pretty much nailed it. In Hebrew, there are only four tenses - imperative, past, present, and future. So there is no "could I have" or "I would like" or anything like that. Those tenses don't exist, and those phrases don't exist. Rather, one literally says "I want X [please]." Of course, that's rude in English, and most languages, but when translating literally to a language that is not their first, it comes out rude.

True story - my Hebrew School went to a local ice cream place once and a teacher from Israel really upset the staff in there by saying something to the effect of "I want vanilla ice cream." That's exactly how you would say it in Hebrew, but not at all how you should say it in English. Good job everyone, especially WiZ for the final solve. My next puzzle isn't coming out until tomorrow night, mainly because it concerns a true story that hasn't happened yet but will tomorrow most likely.